The effects of calcium channel blocking agents on cardiovascular function.

The hemodynamic effects of calcium blocking agents are a composite of the various direct and indirect cardiac and peripheral vascular actions of these drugs on the individual determinants of left ventricular pump function. Calcium antagonists have been shown to have a direct negative inotropic effect, a direct negative chronotropic effect and a direct effect to produce relaxation of vascular smooth muscle and vasodilation. These agents may also elicit important indirect effects by an anti-ischemic action referable to both coronary arterial dilation and reduction in myocardial oxygen demand, as well as a baroreceptor-mediated reflex increase in beta adrenergic tone in response to vasodilation. The net result of these direct and indirect actions on cardiocirculatory dynamics is also dependent upon the individual calcium blocking agent administered, the dose and route of administration, and the underlying status of left ventricular function. Available data do not lead to a clear definition of the hemodynamic effects referable to calcium blocking agents that may be produced by the interaction of all variable factors. At present, however, it would appear that the direct negative inotropic and chronotropic actions of the calcium antagonists are offset by the reflex increase in beta adrenergic tone, in combination with the reduction in afterload produced by the peripheral vascular effects of these agents. Preliminary data suggest that certain calcium inhibiting agents may be useful in the vasodilator therapy of congestive heart failure. Nevertheless, the direct negative inotropic effects of these agents have resulted in clinically evident decompensation in cardiac performance in patients with advanced left ventricular dysfunction, and caution is warranted in the application of calcium blocking agents in this setting.